During the past several decades, plastics have replaced many traditional materials. Among other things, plastics are prevalent in the cardstock industry—which includes articles such as book covers, posters, identification cards and driver's licenses, hotel room keys, gift cards, credit cards and the like. Currently, cardstock articles are primarily made of polyvinyl chloride (PVC) or polyvinyl chloride derivatives. PVC is intrinsically rigid but can be used to form flexible articles through plasticization using phthalates. PVC also possesses excellent mechanical properties and heat resistance.
Despite its attractive properties, PVC is not perceived as eco-friendly. It does not biodegrade readily, is not derived from renewable feedstock, and has no established recycling stream. Furthermore, PVC compositions often release toxic chemicals into the environment, such as phthalates, oligomers, hydrochloric acid or even unreacted monomers. Further, PVC and polystyrene (PS) are made from crude oil and thus are (1) not sustainable and (2) subject to price fluctuations. Since a recycling program has not been established for these types of plastic articles, they are becoming non-degradable wastes, often ending up in landfills or as unsightly litter in the environment.
Many municipalities are currently seeking to ban these rigid plastics (PVC and PS) and consequently there is a strong incentive to find “green” alternatives from renewable resources that are biodegradable and compostable. Several research groups have created cardstock formulations that are biodegradable and compostable, however these formulations are typically brittle and distort when subjected to even low heat.
In U.S. Pat. No. 8,604,123 to Weismann (hereinafter “Weismann”), Weismann formulates a biodegradable polymer composition using the filler calcium carbonate with PLA as a base resin. The polymer formulation is stated to have a heat resistance of 150-250° F. (65.5-121° C.), but Weismann does not disclose supporting data, and the disclosed chemistry does not appear to support Weismann's claim. Those who are skilled in the polymer arts understand that the use of a filler such as calcium carbonate would not have the effect on the heat distortion temperature that Weismann claims. Thus it is not clear to what extent this technology overcomes the inherently poor heat resistant properties evident in past PLA formulations.
In U.S. Pat. No. 6,096,431 to Matsudaira (hereinafter “Matsudaira”), Matsudaira creates a biaxially oriented sheet comprised of polylactic acid (PLA). Matsudaira claims properties close to polyethylene terephthalate (PET) resin sheets and a degradable substrate. However, left in activated sludge, only a slight decrease in weight and mechanical strength was observed. Significantly, the problem with low degradation remains an issue.
The need exists for a cardstock composition made from renewable resources that has an improved heat distortion temperature and is degradable and compostable. Since most cardstock is manufactured using petroleum-based materials such PVC or PS, using renewable biodegradable plastic (specifically PLA) provides environmental advantages. An environmentally-friendly cardstock can be incorporated into a variety of cardstock end products, including products that have a magnetic strip containing stored data. In the current disclosure, the inventors describe a degradable and compostable cardstock comprising a mixture of biodegradable biopolymers, a torrefied biomass component, and a plasticizer. The aforementioned degradable and compostable cardstock in this disclosure was then compared to a commercially available credit card material comprised predominately of PVC.